Ferromagnetic-ferromagnetic-antiferromagnetic-antiferromagnetic correlation and magnetization plateau in spin-1/2 J1-J1-J2-J2 tetrameric chains

The magnetization process of a spin-1/2 J1-J1-J2-J2 tetrameric Heisenberg chain is investigated by the infinite time-evolving block decimation (iTEBD) method. A magnetization phase diagram including three different phases, i.e., a fully polarized (FP) phase, a 1/2 plateau phase, and a spin-fluid (SF) phase, is obtained. All the quantum phase transitions (QPTs) are determined to belong to the second-order category, and the central charge in the critical SF phase equals 1. In addition, a 1/2 plateau phase also exists in the classical J1-J1-J2-J2 tetrameric Ising chain. The F-F-AF-AF (or AF-AF-F-F) type longitudinal correlation is found to be important and necessary for the appearance of the 1/2 plateau state in both quantum and classical cases.